And they have hashtags like Bonespiration, meant to promote being bone thin and emaciated.
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"You see a lot of things that are posted with the intent of glamorizing the disorder," said eating disorder survivor Erika Lee.
Lee showed us her own ultra-thin pictures when she was battling her illness. She used to post online too and says it likely prolonged her recovery.
"It was like the secret rulebook of here's how to get away with this," said Lee.
Years ago, similar tags like, thinspiration, pro- bulimia, and pro-anorexia prompted Instagram to ban accounts and hashtags that promote self-harm.
Experts say the problem is, as soon as one social media site catches up to a hashtag, the posters just change them to something else.
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"It is a bit like whack a mole. A lot of the social media platforms are doing their best to deal with this content in a responsible way, but due to the volume of it and the number of users who are at risk, it is very difficult to manage," said Claire Mysko.
Experts say for the 30 million people in the U.S. who suffer an eating disorder, just seeing the posts could trigger them to fall deeper into an illness.
"Eating disorders have the highest mortality rate of any psychiatric diagnosis. People who are struggling in a very, very dark place," Mysko.
The national eating disorders association works with social media sites.
When we looked up bonespiration on Instagram, for example, we got a warning saying the tags "often encourage behavior that can cause harm, and even lead to death."
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The key, experts say, is support.
"If you're compelled to post content like this to connect with others, please know that there are resources available," Mysko.
Lee says she was able to receive treatment and now she's living a healthy lifestyle.
"There's nothing glamorous about starving yourself until you're emaciated."